A new foundation for the study of bird behaviour: Konrad Lorenz’s ‘Kumpan’ paper of 1935

The Nobel Prize in Physiology or Medicine was awarded to Konrad Lorenz, Niko Tinbergen and Karl von Frisch in 1973 for their pioneering work during the 1930s and 1940s, in the study of animal behaviour. Lorenz established the foundations of ethology in 1935 in what has become known as his “Kumpan paper”. The paper focussed on the social relationships between conspecifics (i.e. ‘kumpans’, companions) and provided a much-needed conceptual framework for the study of animal behaviour. We describe the origins and immediate reception of Lorenz’s paper using his correspondence with colleagues, mainly Erwin Stresemann who was then the influential editor of Journal für Ornithologie. The Kumpan paper was notable for its extraordinary originality, but also for its length and—in parts—its incomprehensible language. Most of Lorenz’s concepts were rapidly superseded as the field of Ethology/Animal Behaviour developed over the following decades. The paper (translated in full into English only in 1970) is rarely read today, but as we show, many of Lorenz’s observations of birds are both timeless and highly original and have the potential to inspire further research today.